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The mirrors used on concentrating solar systems must be able to withstand severe and sustained environmental stresses for long periods of time if they are to be economically acceptable. Little is known about how commercially produced wet process silvered second surface mirrors will withstand the test of time in solar applications. Field experience in existing systems has shown that the performance of the reflective surface varies greatly with time and is influenced to a large extent by the construction details of the mirror module. Degradation of the reflective layer has been seen that ranges from non-observable to severe. The exact mechanisms involved in the degradation process are not well understood from either the phenomenological or microanalytical points of view and are thus subject to much debate. The three chapters of this report summarize the work recently performed in three general areas that are key to understanding and ultimately controlling the degradation phenomena. These areas are: a survey of the present commercial mirroring industry, the microanalytical examination of numerous degraded and nondegraded mirrors, and an investigation of several novel techniques that might be used to extend the life of heliostat mirrors. Appendices include: (a) list of mirror manufacturers and (b) recommended specifications for second surface silvered mirrors for central receiver heliostat applications. (WHK)

The protonation of the 1,2(4H)-diazepines 2a, 2b, and the 1,2(1H)-diazepine 3a in various acidic media has been studied by u.v. and n.m.r. spectroscopy. Compounds 2a and 3a undergo protonation to g...

It is generally believed that grain boundary impurities contribute to intergranular fracture in the presence of hydrogen by either; 1) decreasing the intergranular cohesion; 2) enhancing hydrogen absorption along grain boundaries; or 3) a combination of both processes. A comparison of the relative effects of S, Sb and P on the intergranular fracture of iron and nickel has been completed1,2 and will be summarized in this paper. With sulfur as a bench-mark, the effect of S, Sb and P on the intergranular fracture of iron and nickel at cathodic potentials can be expressed by the following equivalent grain boundary sulfur concentrations, Cs: $$C_s^{eq}\left( {Fe} \right) = 5 Sb + S + {\gamma _P}P{\gamma _P} > 0$$ (1) $$C_s^{eq}\left( {Ni} \right) = Sb + S + 0.07P$$ (2)

Thermolysis of 3,5,7-triphenyl-1,2(4H)-diazepine (1) gives, besides the known 2,4,6-triphenyl-pyridine (2), 3,5,6-triphenyl-1,2(4H)-diazepine (3) and 3,5,6-triphenyl-1,2(1H)-diazepine (4) whose str...

The purpose of this paper is to present data showing an increased adsorption rate for H2S on plastically strained iron. There has been considerable speculation in the literature concerning the effect of strain on enhanced corrosion and surface reactivity, but there has been no direct experimental evidence that strain does increase surface reactivity. To understand the possible effects of strain enhanced adsorption on crack initiation and growth is the main motivation for these studies. It is also possible that strain enhanced adsorption may be important for catalytic, corrosion and wear properties of materials.

The grain boundary chemistry of reaction bonded silicon nitride (RBSN) and the effect of iron species and content on this chemistry is investigated using X-ray Photoelectron Spectroscopy. RBSN specimens were fractured in-situ and the shape and energy of the Si, N, C, O, and Fe photoelectron peaks were examined and compared for the range of specimens. Data are reported for semiconductor grade RBSN, Fe-doped semiconductor grade RBSN, and metallurgical grade RBSN specimens. Results indicate that the grain boundaries have an elemental composition of Si, N, O, and C; however, there are important chemical differences depending on the purity of the starting material. In the RBSN made from metallurgical grade silicon, the grain boundaries have a distinct ''oxide-like'' layer, with a subregion of Si/sub 3/N/sub 4/. No distinct oxide layer was observed in the RBSN made from semiconductor grade silicon, where the O appears to be uniformly incorporated into the Si/sub 3/N/sub 4/.

SummaryAdministration of mouse brain interferon prior to or after inoculation of 100-250 LD50 of encephalomyocarditis (EMC) virus, conferred a significant degree of protection on weanling IC mice. Continuation of interferon treatment for several days after virial inoculation considerably increased the number of mice surviving infection. Most interferon protected mice did not develop HI antibody to EMC virus nor did they demonstrate resistance to viral rechallenge. By acting early in the course of viral infection interferon may have repressed viral multiplication below a level necessary to induce a specific immune response. Mice did not develop a “tolerance” to repeated inoculation of exogenous interferon. Considered together the experimental results suggested that continued interferon administration may prove of value in the treatment of some viral diseases.

In the use of vibrating quartz crystals as vacuum microbalances, two extremes of sensitivity have been used to advantage. Commercial instruments have been successfully employed in the low-sensitivity region to measure evaporated deposits equivalent to one hundred atomic layers or more. At the opposite end of the sensitivity spectrum, extremely sensitive arrangements have been employed for gaseous adsorption studies. In the intermediate range required to continuously monitor deposits ranging from fractional monolayers to several atomic layers (e.g. germanium), a difficulty arises because of thermal shocking of the crystal. Thermal gradients established by the absorption of radiant energy from the evaporant source can result in frequency changes larger than those due to the mass loading under study. These frequency changes are quite reproducible from one crystal to another, thus permitting the elimination of the spurious changes by observing the beat frequency of two similarly shocked crystals. If only one of the crystals is allowed to receive a deposit, the beat frequency measurement can be used as the criterion of mass loading, thus allowing the direct detection of very small deposits. Such an arrangement employed in an ultra-high vacuum evaporation experiment is described in this paper. Bei der Verwendung von Schwingquarzkristallen als Vakuum-Mikrowaagen wurden zwei extreme Empfindlichkeitswerte ausgenutzt. Die auf dem Markt erhaltlichen Instrumente wurden dazu verwendet, um in der Gegend niedriger Empfindlichkeit aufgedampfte Niederschlage zu messen, die 100 oder mehr Atomschichten entsprachen. An dem entgegengesetzten Ende des Empfindlichkeitsspektrums wurden zur Untersuchung der Gasadsorption extrem empfindliche Anordnungen benutzt. In dem Zwischengebiet, das dazu benutzt wird, um Niederschlage von Bruchteilen einer Monoschicht bis zu einigen Atomschichten (z.B. im Falle von Germanium) fortlaufend zu verfolgen, gibt es infolge des thermischen Schocks des Kristalls gewisse Schwierigkeiten. Thermische Gradienten, die durch die Absorption von Strahlung seitens der Verdampfungsquelle hervorgerufen werden, konnen zu Frequenzanderungen fuhren, die grosser sind als die, die sich aus dem Auftrag der Masse, die untersucht werden soll, ergeben. Derartige Frequenzanderungen sind von einem auf den anderen Kristall durchaus reproduzierbar und gestatten auf diese Weise die Eliminierung der geringfugigen anderungen dadurch, dass die Taktfrequenz von zwei in gleicher Weise dem Temperaturgradienten ausgesetzten Kristallen beobachtet wird. Wenn die Anordnung so getroffen ist, dass von diesen beiden Kristallen lediglich einer Masse erhalten kann, dann kann die Messung der Taktfrequenz als ein Kriterium fur die Massebeladung verwendet werden, so dass sehr kleine Belage direkt festgestellt werden konnen. In dieser Arbeit wird eine derartige Anordnung beschrieben. Die Aufdampfexperimente wurden im Ultrahochvakuum durchgefuhrt. Dans l'utilisation des quartz vibrants comme microbalances sous vide on a exploite avantageusement les deux extremites de la gamme de sensibilite. Les appareils du commerce ont ete employes avec succes dans le domaine des faibles sensibilites pour mesurer des depots obtenus par evaporation s'elevant a une centaine de couches atomiques ou plus. A l'extremite opposee de la gamme de sensibilite, on a utilise des appareils particulierement sensibles pour des etudes d'adsorption de gaz. Mais, dans le domaine intermediaire qu'il faut utiliser pour le controle en fonctionnement continu de depots pouvant etre constitues d'une fraction de couche monoatomique a plusieurs couches atomiques (par exemple le germanium) on se heurte a des difficultes dues au choc thermique que recoit le cristal. Les gradients thermiques provenant de l'absorption de l'energie rayonnee par la source d'evaporation peuvent entrainer des variations de frequence plus importantes que celles qu'entraine la masse du depot etudie. Ces variations de frequence sont tout a fait reproductibles d'un cristal a un autre, et c'est ce qui permet d'eliminer ces parasites en se basant sur la frequence de battement de deux cristaux subissant un choc thermique identique. Si le depot n'est fait que sur un des cristaux seulement, la mesure de la frequence du battement peut etre utilisee comme repere de la masse deposee, ce qui permet de detecter directement de tres petits depots. Cette communication donne la description d'un dispositif de ce genre utilise dans une experience d'evaporation sous ultra-vide.

Repeated administration of potent mouse interferon preparations increased the survival of Balb/c and C 57/B1 6 mice inoculated with 2,000-3,000 RC 19 and EL 4 tumor cells. Only 7/188 (3.7%) untreated mice (or mice treated with control preparations) survived more than 22 days after intraperitoneal inoculation of RC 19 tumor cells. None survived more than 60 days. In contrast, 101/103 (98%) interferon-treated mice survived beyond 22 days, and sixteen (15%) survived more than 60 days. None of these 16 surviving mice show any sign of tumor at present. Three mice (of the 16) from an early experiment are alive ten months after inoculation of RC 19 tumor cells. Mouse interferon preparations derived from three different tissue sources— brain, serum, and monolayer cell cultures (with Newcastle disease virus and West Nile virus as interferon-inducing agents)—all proved effective. A purified preparation of mouse brain interferon was as effective as crude brain interferon. Human amniotic membrane interferon and control tissue preparations were without effect. These findings suggest that interferon itself (or a factor closely associated with interferon) is the active moiety in these preparations.

SummaryThe efficacy of endogenous, exogenous, and combined endogenous-exogenous interferon was compared in the treatment of mice preinfected with 40–80 LD50 of EMC virus. The different interferon inducers, Newcastle Disease virus, statolon, and poly (I) poly (C) proved equally effective in increasing the survival of viral infected mice. Daily reinoculation of an inducer afforded no significant added protection. Administration of potent interferon preparations proved more effective than any of the interferon inducers in 3 experiments and equally effective in a fourth experiment. In 2 experiments no significant difference was observed between the therapeutic efficacy of combined endogenous-exogenous interferon and exogenous interferon alone, whereas in a third experiment the combined treatment proved more effective. A combined interferon treatment initiated 18 or 24 hr after inoculation of 2.5 or 8 LD50 of EMC virus still afforded a significant degree of protection.

SummaryA sensitive assay of the anticellular action of mouse interferon preparations is presented. This technique is based on the inhibition of L 1210 cell colony formation by interferon preparations incorporated in an agarose nutrient medium base.

(D, T) neutrons have sufficient kinetic energy for various nuclear reactions such as (n,α), (n,p), and (n,2n) to occur. A series of experiments have been performed using a 14.8 MeV (d, t) neutron source in which the radioactive daughters ejected from the near surface region of the target material have been collected and measured. The geometry of the experimental arrangement was such that radioactive daughters ejected in the forward direction (neutron current direction) and backward direction were collected. For example, the forward radioactive sputtering ratio for 92mNb produced by the 93Nb(n,2n) reaction from cold‐worked niobium foil is (1.06±0.06) 10−7 radioactive atoms/neutron, and the backward sputtering ratio for 92mNb is (7.58±1.09)10−10 atoms/neutron. For annealed gold the forward sputtering ratio for 196Au produced by the 197Au(n, 2n) reaction is (1.05±0.06)10−7 atoms/neutron, and the backward sputtering ratio for 196Au is (2.83±0.09)10−9 atoms/neutron. These sputtering ratios are the slopes of me...

Experiments to determine the material removed (sputtering) from the surfaces of metal foils during irradiation with 14.8 MeV (d, t) neutrons will be described. Neutron activation analysis was used to measure the sputtered material. This is an integral technique which determines quantitatively the number of atoms on the collector. Six experiments were done using the Lawrence Livermore Laboratories rotating target (d, t) neutron source and one experiment was done at the (d, Be) source at the University of California, Davis. In each experiment a large number of collector–target assemblies were located at various distances from the neutron source. The collector–target assemblies were housed in a stainless steel ultrahigh vacuum system and all irradiations were performed in a high‐vacuum environment [∠1×10−7 torr to 5×10−9 torr (∠1.3×10−5 Pa to 6.5×10−7 Pa)]. For these experiments the mean (d, t) neutron energy was 14.8 MeV in the forward direction, and for the different beam‐on times and various source to sam...

Photolysis of the methyldiazepine (5a) led directly to the pyrazole (7) whereas the ethoxycarbonyl- and acetyl-diazepines (5b) and (5c) gave cycloadducts (6b) and (6c); thermolysis of the diazepines (5) or the diaza[3,2,0]bicycloheptadienes (6) produced mainly ylides (8) and small amounts of 2,4,6-triphenylpyridine (9), except for (5a) which yielded (9) only.

Protonation of 3,5,7-triphenyl-4H-1,2-diazepine, (1), previously believed to give cation (3), has been shown by n.m.r. study to give (5) or (6).